Well integrity is becoming a key area of focus for most well operators during the entire well life cycle. To ensure safe operation of oil and gas wells and to avoid blow-out incidents or leakage of hydrocarbons to the environment, the integrity of the well downhole structure (tubing, casing, packers, barriers, and other structures) is of utmost importance. Recent mishaps/events in oil and gas industry stress the importance of well integrity evaluation and maintenance, where leak detection, isolation, and quantification form a major part. Hence, reliable leak detection and remediation/mitigation is important to avoid its adverse effects on the environment.